The present invention relates to power management in wireless local area networks (WLANs), and more particularly to a dynamic per-client power management in WLANs.
Wireless local area network (WLAN) is an important technology, for providing Internet access to users. Managed WLANs refer to deployments in which all access points (APs) are under the same administrative domain. Example of such managed WLANs include small-range corporate networks and campus networks, hot-spot networks, such as T-mobile, and city-wide networks, such as Google's Wifi, MIT's roofnet, and Houston's urban network. In order to provide maximal coverage, such networks often contain multiple APs with overlapping transmission and frequency ranges. While coverage depends on the transmission ranges of the APs, the performance of each AP depends on the inference ranges of neighboring APs. Greater overlap of interference and transmission ranges can lead to increased contention for transmission channels and increased packet collisions. As a result, in a dense deployment of APs for maximal coverage, each AP often operates at sub-optimal performance due to interference from neighboring APs, thereby reducing overall network throughput.
Conventional approaches for mitigating interference and improving spatial reuse (i.e., increasing the number of simultaneous AP-client transmissions) include using non-overlapping transmission channels for interfering APs, and tuning each AP's transmission power to an optimum level. The approach of using non-overlapping transmission channels suffers from a scarcity of non-overlapping channels in the 802.11a/b/g standard, which is commonly used for WLANs. The approach of tuning each AP's transmission power level to an optimum level requires an AP to use the same power level to transmit to all of its clients.